1. Field of the Invention
The present invention relates to an electro-photographic image forming apparatus and method of using the same. More particularly, the present invention relates to a fusing device installed in an electro-photographic image forming apparatus that applies heat and pressure onto an image so that the image can be fused to the paper and a method of using the same.
2. Description of the Related Art
In general, an electro-photographic image forming apparatus includes a fusing device that applies heat and pressure onto an image transferred onto paper so that the image can be fused onto the paper.
A heating unit 12 with a halogen lamp is installed in a center portion of the fusing roller 11. A surface of the fusing roller 11 is coated with a coating layer 11a comprising polytetrafluoroethylene. The heating unit 12 generates heat in the fusing roller 11 and the fusing roller 11 is heated by radiant heat generated by the heating unit 12.
The pressurizing roller 13 is resiliently supported by a spring 13a, and thus, capable of applying pressure onto the paper 14 passing between the fusing roller 11 and the pressurizing roller 13 so that the paper 14 can contact the fusing roller 11. Accordingly, when the paper 14 passes between the fusing roller 11 and the pressurizing roller 13, predetermined pressure and heat are applied onto a powder toner image 14a transferred to the paper 14. Thus, the powder toner image 14a is heated and fused onto the paper 14 by the predetermined heat and pressure applied by the fusing roller 11 and the pressurizing roller 13.
Use of a conventional fusing device, such as the fusing device 10 shown in FIG. 1, that adopts a halogen lamp as a heat source causes unnecessary power consumption. Accordingly, when no print job is required, the conventional fusing device is turned off to reduce its temperature. For this reason, when the conventional fusing device is turned on to perform a print job, it takes a long time to warm up until its temperature reaches a fusing temperature.
Since a fusing roller of the conventional fusing device is heated by radiant heat generated by the heat source, a heat transfer speed is slow. Also, since the heat of the heated fusing roller is delivered to paper when the paper contacts the fusing roller, it is impossible to timely compensate for a deviation in temperature caused by a reduction in the temperature, thus preventing adjustment of temperature dispersion.
Also, a nip caused when a pressurizing roller contacts the fusing roller has a narrow width, and thus, there is a limitation to forming an image at a high speed. To solve this problem, the nip width is increased by the diameter of the fusing roller or the pressurizing roller. However, in this case, the volume of the fusing device is increased.
To solve this problem, a fusing device with a continuous belt has been introduced. For instance, published Japanese Patent Publication No. 2003-156961 discloses a fusing device that includes a fusing roller that includes a heat source therein, and a continuous belt rotated while being supported by three rollers, facing the fusing roller. One of the three rollers is pressed toward the fusing roller due to a spring force, thus applying pressure onto the fusing roller, and a part of the continuous belt contacts and applies pressure onto the fusing roller by a pressure support pad. Thus, when paper with an image passes through a contact portion between the fusing roller and the continuous part, the image is heated and fused onto the paper.
Published Japanese Patent Publication No. 2002-182500 discloses a fusing device with a continuous belt, using electromagnetic induction. The fusing device includes the rotating continuous belt being supported by two rollers and a pressurizing roller that faces the continuous belt and is rotated to apply a pressure onto the continuous belt. An induction-heating unit that includes an induction-heating coil therein is installed on an inner surface of the continuous belt. A flux change in the induction-heating unit allows heat generated in a magnetic layer formed on the continuous belt to be delivered to paper passing through a contact nip between the continuous belt and the pressurizing belt, thereby fusing an image, which is transferred to the paper.
However, a high-thermal-capacity elastic layer of the continuous belt of the fusing device disclosed in published Japanese Patent Publication No. 2003-156961 is minimized, thus lowering the thermal storage capability of the fusing device. For this reason, the fusing device is inconvenient to use since it needs to be frequently charged, thereby increasing power consumption and causing flicker.
Also, the fusing device using electromagnetic heating, disclosed in published Japanese Patent Publication No. 2002-182500, requires the continuous belt to include a magnetic layer, thereby increasing manufacturing costs.